Update readme

Signed-off-by: Alex Forencich <alex@alexforencich.com>

README.md

@@ -95,6 +95,9 @@ To facilitate the dual-license model, contributions to the project can only be a
     *  I2C slave AXI lite master
     *  MDIO master
     *  UART
+*  PCI Express
+    *  PCIe AXI lite master
+    *  PCIe AXI lite master for Xilinx UltraScale
 *  Primitives
     *  Arbiter
     *  Priority encoder